Triangulation conundrum

[LizzieL]

I have two Common Ancestor matches on my mother's side who triangulate with me.
One is CD with a match of 43cM over 3 segments and the other is SW with a match of 90cM over 6 segments. I have compared them on a chart (Derham-King1). This shows CD as my 4C1R and SW as my 3C1R, which seems in line with the DNA match results, one being about half the other. CD's line is from her own tree on Ancestry. BUT, if this was the correct tree, CD and SW would have no genetic relationship with each other, and there would be no triangulation between the three of us. Prior to CD doing a DNA test, I had her on my tree but in a different place. (See Derham-King2). That makes her a 3C1R, and all 3 of us are descended from MAK (Mary Ann King), so fits the triangulation. But since I have the same relationship with both her and SW, I am surprised our DNA match levels are so different. Higher for me and SW where I only share King DNA, than for me and CD where we share both Derham and King DNA. Could it be that SW and I have a second relationship through different common ancestors that I haven't discovered yet? 90cm seems a bit high for 3C1R according to DNA painter. Any ideas, pleas?

[Petros]

As you say 90 cM is a bit high for a 3C1R. However, amongst the many descendants of my GGGF i have two 3C1R who are 92 and 95 cM matches on Ancestry. They are descended from different children of my GGGF. These two matches are actually higher matches than 4 of the 5 3C matches from that GGGF!

[Biggles50]

90cM is a perfectly viable DNA share for a 3C1R.

I have one at 91cM, another at 109cM and another at 113cM

Not via Thrulines but both via well researched and compared branches, plus contact with all three to compare notes and verify each others links.

A 3C1R does have a 0-192cM range of possibilities with a 48cM mean share.

I have many 3C’s who share about 50cM with me such is the wide range of relationship possibilities.

[familydar]

Are you certain they triangulate on the same segments?  If you're looking at Ancestry, where (unless things have changed) you have no way of knowing which position(s) on which chromosome(s), it's entirely possible that you share 3 segs with CD and 6 segs with SW, but that CD and SW share completely different segments with each other.  They have a common ancestor but not necessarily the one that either of them shares with you.

Jane :-)

[LizzieL]

We all tested with Ancestry so no chromosome browser and no way of knowing whether the three segment CD shares with me are three of the six I share with SW.
 

[Zaphod99]

You could upload to Gedmatch and use the chromosome browser there.

Zaph

[LizzieL]

You could upload to Gedmatch and use the chromosome browser there.

Zaph

I have but the other two haven't and don't reply to messages