You just keep giving them prey u caught and when u have 4 hearts or whatever, you buy a bouquet from the café and then you give them more until you have 4 of whatever is next in the mate thingy, then you give them a diamond from the café and when you have 4 of the next mate icon thingy, they will start sleeping with you and one day, they wilkl ask you if you wanna have kits\puppies someday, you say "yes" and soon you will find you had kits\pups
Hope this helps!!!