Marmosets are almost always born as fraternal twins; cells exchanged during development produce siblings that are a mixture of one another’s cells. DNA testing showed that about half of male marmosets carry a mixture of sperm cells, and some marmoset babies inherit the DNA types of their uncles.
“Germ-line Chimerism and Paternal Care in Marmosets (Cllithrix kuhlii)” by C.N. Ross, J.A. French, and G. Orti, Proceedings of the National Academy of Sciences (volume 104), April 10, 2007, pages 6278-6282.