Lemme try to be a messenger of peace of sorts. (or maybe messenger of piss, if I'll fail)
Bad Dragon:
Develop sexual maturity in matter of hours, as demonstrated by lovely maid 'assistant'.
Very hard to tell of his mental maturity. It takes him a few weeks to gain speech beyond dropping single words - and even then he drops one-liners. His thought process in practice heavily depends on our input - in part, we think for him. He may be a cunning man-wyrm or dumb horny teen depending on our choices. But it seems that eventually he's monomaniacally focused on things like harem, hoard and power with very few interests beyond those fields. His personality is, in a way, partial compared to that of a human, underdeveloped in many areas.
I don't think we can accurately measure his maturity. He's not human and does not seem to share human thought process to a great degree. Given his dependency on our choices, I'd wager his mental maturity may wary.
His Cute Naga:
Develop sexual maturity in matter of weeks. As demonstrated by her absolutely Alabamian interaction with daddy dearest. (cue to obligatory 'Sweet home Alabama!')
Malice is an interesting (and cute) little cookie. We see her act like a curious if unruly child, we see her becoming rowdy teenager and we see her mature into young adult. I think, that's were she stops as of now - she's definitely no longer a naïve child, but still very playful and rowdy.
I would say, she mentally grows into a young adult. I don't think she's fully mature, as in adult proper, but mature enough to be a responsible sexual partner. She seems to understand the birds and the bees well enough, IMO.
So, in rather downer (in)conclusion, I don't think we may gauge their age properly. Our judgement on the topic is clouded by hyper-growth shenanigans, probable inhuman thinking and question of personal traits potentially taken for sings of maturity, etc.
It may be entirely possible that if you choose to wed Malice, she's the older one in the couple at that point.
Anyway, Malice time. Because I just can't have enough of Ravager.
View attachment Ravager - Mali Christmas by 4MinuteWarning.mp4
Padoru~ Padoru~
P.S., to the one who knows. Please, don't get marco on me, lol. Made my day, BTW. Still laughing.