well they did mate in my tank so i think i know who the father was(although you cant really tell with guppies).
for some reason he died about a week later. he was pretty big and i asume he was old when i got him. he had a nice long tail cobra patterned tail and skin with yellow and black on the tail. and sort of a blue and green pattern on the body. if those were the two that mated they should be really pretty babies