From your pic he looked to be a "lower swordtail" guppy.  Like my original one that I bought. Hadn't seen any in a long, long, time, mostly delta tails.

I did use him to breed because I wanted others with the lower swordtail, and matching dorsal.

You can check out my diary where it shows what I did. And admittedly, I got sidetracked with the breeding when "purple" babies started to show up.

Anyway, I think it took seven generations for me to get a lower swordtail. And I have two that I think will be just like great,great....,great,grandpa. He had a long orange tail, and a matching long orange dorsal fin. The little ones are still too young to tell of what they will look like when full grown. (The tails seem to take longer to develop in this variety)

Along the way, I got double swords, delta's, snakeskins????, "purples", and others.

If you want me to tell you what to expect if you mate him, my answer for guppies like this remains,
"Almost anything".

I will try to get some picture of the ones that I have though, and you can see them.
I probably won't have time until after the holidays though.

I think one will have a white lower sword, and matching dorsal, and the other will have orange.
I hope.