In the 3 minion movies i.e. Despicable Me 1, Despicable Me 2 and Minions, all the minions were male characters (including maid Phil :P). Why was not a single female minion character present?
There are no female minions, apparently.
There's an article in The Wrap from July titled
In it, it is explained:
For the French animator, who co-directed the new film with Kyle Balda, the masculine-only nature of the Minions owes to their all-around cloddishness. “Seeing how dumb and stupid they often are, I just couldn’t imagine Minions being girls,” he told TheWrap.
As to their ability to reproduce the article says:
Coffin has said that the creatures cannot reproduce or divide themselves, leading to at least two competing theories.