My cousin has been going with this girl, 'C' for 6 yrs. 'C's family said that she was sleeping with my cousins best friend. When my cousin came back from school 'C' got pregnant and gave the child my cousins last name. Everyone said that the baby didn't look anything like either one of them. We were hearing that 'C' was still messing around with the best friend. 'C' got pregnant again, 2 wks before she delivered, she asked could her mom go into the deliverly room instead of my cousin. My cousin cut the cord on the 1st child. Her mother was in the room at the time of deliverly, and the boy child was given 'C's last name. The children are 13 months apart, they both have different last names even though they are suppose to have the same mom & dad. He's a little mad, because he wondering why they both don't have the same last name weather it be hers or his. Everyone tried to convince my cousin to get a DNA test but he won't. Does anyone know of a home DNA test or website?

If the mothers are sisters and the possible fathers are brothers, can a DNA test determine that the cousins are related through the fathers as well?