What is my mom's cousin to me?
Your mom's first cousin is your first cousin once removed. You share great-grandparents, and that relative sits one generation above you. Their child would be your second cousin.
Answer
First cousin once removed
Path: You → Mother → Cousin
Cousin degree equals min(3, 2) − 1 = 1. Removal equals |3 − 2| = 1. Person A is 3 generations from the shared ancestor; person B is 2 generations away. Along this path, you are 3 generations from the shared ancestor (great-grandparent), and the other person is 2 generations from that ancestor.