No, one tree on its own is fine. Generally, Acers are capable of fertilizing their own flowers without any other Acer tree nearby, if its lots of fertile seeds you're looking for. Some Acer flowers actually change between male, female and hermaphrodite (and possibly back again) over time, but there's certainly no need to worry whether you have a male or female tree for either reproductive or appearance purposes.
Acer rubrum is considered to be divided between male and female trees, but the flowers are either unisexual or bisexual on both, so for reproductive purposes, its not an issue - more reading about that here if you're curious https://en.m.wikipedia.org/wiki/Acer_rubrum#Description
Sorry, I didn't realise you'd commented - missed it altogether, didn't know it had been added into the question either, just happened to notice editor's comment above. In answer to that, the 'many babies' could be the progeny of one or both the trees, there's no way of knowing - most likely from both.