It is possible for a child to have matches that their parents do not due to compound DNA segments. If one segment from each parent is adjacent and the child inherits both, the result is a compound segment. This resulting compound segment looks like one larger shared segment that matches with a cousin.

Mother, Mari Onni    
Name SNP Set
. 2
0
0
4
2
0
0
5
2
0
0
6
2
0
0
7
2
0
0
8
2
0
0
9
2
0
1
0
2
0
1
1
2
0
1
2
2
0
1
3
2
0
1
4
.
Half Identical Region Match Non-Match
Mari Onni
Matching Cousin
Father, Peter Wiscured
Name SNP Set
. 2
0
0
4
2
0
0
5
2
0
0
6
2
0
0
7
2
0
0
8
2
0
0
9
2
0
1
0
2
0
1
1
2
0
1
2
2
0
1
3
2
0
1
4
.
Half Identical Region Match Non-Match
Peter Wiscured
Matching Cousin
Daughter, Margo Wiscured
Name SNP Set
. 2
0
0
4
2
0
0
5
2
0
0
6
2
0
0
7
2
0
0
8
2
0
0
9
2
0
1
0
2
0
1
1
2
0
1
2
2
0
1
3
2
0
1
4
.
Half Identical Region Match Non-Match
Margo Wiscured
Matching Cousin

This may lead to the child having matches that the parents do not. The probability of this happening is dependent on the degree of shared ancestry between the parents. The more shared ancestry they have the more likely their children will have compound segments.

For example, Margo Wiscured is the daughter of Peter and Mari (Onni) Wiscured. She shares a 5.19 cM block on chromosome 6 and another five small segments for a total of 19 cM with Ed Blet. The program calculates Ed to be her 5th – Remote Cousin. Ed is not on the match lists of Margo’s parents.

Upon indepth evaluation, Margo’s mother Mari shares several small matching segments with Ed Blet. One of these is the SNP Set #2012 that runs from 1525402 to 1525603. This is a small amount of DNA and is only about .81 cM. Mari and Ed share additional small segments for a total of 15.37 cM. Although they do have common ancestry, it is well before the genealogical period.

Margo’s father Peter shares a common segment with Ed Blet that starts at SNP Set #2006 and ends at SNP Set #2011. This forms a small segment that runs from 112510 to 1524189 and is 4.39 cM. Peter and Ed also share other small segments for a total of 18 cM. The likely source is a remote relationship that predates the genealogical time frame.

By coincidence, the two smaller segments from each of Margo’s parents have formed a compound segment that looks like a larger segment. Because Margo also inherited many small shared segments (with Ed) from each parent, the program triggers a match calculation for her but not her parents.

Such matches will most often fall into the Speculative Relative category. The true relationship will be on the more remote end of the range. That is, the parents and the child almost surely share a relationship with the remote cousin within twenty generations. However, the relationship is unlikely to be from genealogical times.

This is one reason we recommend that matches in the Speculative Relative category only be used to evaluate matches between known cousins, i.e., 5th through 8th cousins on a documented lineage. You might also consider them when many family members share the same suggested relationship.

Note: The bioinformatics team periodically reviews the start and stop points for the blocks. They may be different from the examples used here.