There are no particular age criteria for any queer person to come out as open from being closeted and it is always considered one of the crucial yet intense decisions by any person from the queer community because the whole perspective of how others see changes, sometimes good and unfortunately sometimes bad too but coming out is inevitably a good decision even though some bad consequences and complications remain inescapable. Some people come out open to society first and then slowly open up themselves to near and dear. No matter how strong a person is, coming out to one's parents as queer is an emotional task and one must evaluate too many things before pulling together to express one's identity and orientation, especially when they are against typical gender norms and sexual preferences.
If you are open then, you must already be knowing what it took for you to come out as a queer person to your parents. If you are open and didn't get accepted by your parents yet, then you must be still struggling to convince them. If you are closeted then, you must be in a deep dilemma about whether to come out or not. Parents are the most constant relation for any person regardless of how far they are and no matter how bad the rapport is. Hence, any queer person needs to remember a few things before coming out while coming out and even after coming out as a queer person.