Can my half uncle's, half sister be my 1st cousin once removed?

Question

What we believe to be my half-uncle (16% shared DNA | 1,118 cM), has a believed half-sister (1,660cM). My relation to the 'half-sister' is (8% shared DNA | 541 cM) which would most likely make her my 1st cousin 1x removed. They are both about 30 years older than me. My father was adopted (died in 2012), and we believe they all share the same father making me a half-niece.

Is this possible with having so little cM/DNA with the woman?

Answer 1

DnaPainter is a great tool for answering questions like this.

Plugging in 541 cM (like I did above) gives the following possible relationships:

• 88% Great-Great-Aunt / Uncle Half Great-Aunt / Uncle Half 1C 1C1R Half Great-Niece / Nephew Great-Great-Niece / Nephew
• 10% Great-Grandparent Great-Aunt / Uncle Half Aunt / Uncle 1C Half Niece / Nephew Great-Niece / Nephew Great-Grandchild
• 3% Half GG-Niece / Nephew † Half GG-Aunt / Uncle † 1C2R † Half 1C1R † 2C

"Half Niece" is definitely on that list. (in the 10% bin)