There are a number of ways to handle adoption, fostering, and other similar kinds of relationships in genealogy.  Keep in mind that in most genealogy programs, the tracking is for biological and marital relationships only.  However, many researchers are more family historians so they do research and track these non-biological relationships. According to some families, the non-biological children of a family are as much a part of their family as if those children were actually born to both parents.  So whether one parent or both parents is/are not the biological parent(s) of a child, both parents consider the non-biological child as own their son or daughter.  In addition, any other children in the family usually consider all children in the family as their full siblings (childhood squabbles and stories notwithstanding).

Therefore, there needs to be some way to show the non-biological relationships along with the biological ones. Because most genealogy programs follow a somewhat standard way of creating narrative reports that do not provide well for non-biological children, the family historian must often provide other means so that non-biological children are included in reports.

As noted, for most programs and their reports, children are either assigned to their biological or their non-biological parents depending on the focus of the report being run.  So, if an adoptive, foster, or step child is to be included  in a report, the question must first be answered as to who is the initial focus of the report and how is the child to be included.  If the child is to be shown with the biological family, then the biological parents should be assigned as the parents of the child.  But if the child is to be shown with the non-biological parents then they should be assigned as the child's parents.

The problem comes when both sets of parents are included as part of the report.   Take for example this situation, the focus of the report is the child's grandparent and one biological parent is a child of the grandparent and an adoptive parent is another child of the grandparent (e.g., a brother or sister adopting their sibling's child).  In this case, the family historian wants to include the child in some way within the biological parent's family and within the adoptive parent's family.  Then there are situations where cousins have married and/or adoptions occurred in a similar way. One can always add notes to provide the details and show the child normally with one family and in the note of another family.  That is not always desirable, but is about the only reasonable way things can be done.

In TMG, a child may have only one set of Primary parents, but may also have non-Primary parents.  The non-Primary parents may be assigned temporarily as the Primary parents and vice versa.  Thus the family researcher may print a report whose focus is the family of the biological line and the child would be shown there properly. Later, the researcher may create a similar report on the non-biological parents also showing the child.  This requires the researcher to "change" the Primary parent assignment as needed prior to producing a report and the change is somewhat simple to make. So the researcher must decide which set of parents should be assigned normally as the Primary parents and which as the non-Primary parents.  For example, the biological parent(s) are assigned as Father-BIO and/or Mother-BIO and the (say) adoptive parent(s) as Father-ADO and/or Mother-ADO.  Then one set is assigned as the Primary parents while the other set is left as non-Primary parents.

Another provision in TMG, similar to the note method, is available. All parents are assigned as above with the biological parents assigned as Primary.  With the child as the focus person in the Details window, the Adoption Tag is assigned with the child as Principal #1.  The date and place of the adoption are entered as usual, if known. Then the adoptive parent(s) are assigned as Witnesses.  The Tag (e.g., child's) Sentence and the Witness Sentences for both adoptive parents are adjusted as needed.  The Sentences might be as follows:

Note that the Witness Sentence for both parents is the same.  There may be situations in which they are different.  This would be true where one parent was adoptive and the other was a biological parent. Depending on the state laws and how the Court ruled on the adoption, the biological parent may also be adopting their own child. In such a case, adjust the Sentence Structure for that parent as you consider necessary.

The above is designed to show the child in the proper relationship for both families.  The problem is that the adoptive child may not show later in reports and thus continue to show the child's descendants.  This would be true if the child is only shown as adoptive and is not included as a biological child in some other family of the report.  For these situations, it may be desirable that the adoptive parents are the Primary parents and the Adoption Tag show the biological parents instead of the adoptive parents.  The Tag and Witness Sentences would, of course,  need editing to show this situation properly -- maybe something like:

So, either way, the child could be shown in a report with the proper entries and continue to show their descendancy if that is needed.

In some cases, you may wish to show both sets of parents as Witnesses to the adoption.  If you do, you should probably assign Roles to the Adoption Tag.  For example, you might create Roles like Bio-Father, NBio-Father, etc.  Then you would also adjust the Tag and Witness Sentences as needed to show the parents in their correct relationship to the child.

Note that all the above speaks of adoptions as opposed to step, foster, guardian and other relationships -- including god-parents and children.  For these relationships, the family historian may or may not wish to include the child in later parts of the family.  But the above treatment of adoptive relationship can also be used for these other relationships in exactly the same way.  The TMG user will want to adjust the Tag and Witness Sentences as appropriate for those situations.

So the TMG user has a lot of options for all the different relationships that are likely to exist.