As long as ones a female, you shouldnt have probs. with them being together. Keep an eye on them. If you seem them fight nip or signs of blood separate them. Also makesure neither one is hogging all the food.
If you are planning on breeding them, make sure they are the right size first. Wheight is more important than age when it comes to breeding leos and some don't even reach maturity until a certain wait. The min. they should wheigh if you breed them is about 40 grams. this means they are healthy, especially the female since it is hardest on her. But since you said they are only 25 grams, you probably don't have to worry about premature breeding. I hope this can help.
Ed