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.
Don't think that every coming-out story would end up in tragedy and disappointment. Some can be celebrated and appreciated too. So, don't assume the result without even testing the waters. But you must be cautious enough regarding the unforeseen consequences. Be confident enough to declare what you are instead of sounding confused, disgusted and embarrassed. If you sound low about your identity, then how can you expect your parents to feel comfortable, safe and confident about you?
Don't get succumbed to peer pressure or get along with people's influences around. Analyse the possibilities before coming out just because other people force you to, most importantly it is always good to consider how your parents react. Accordingly, try to develop the process easier by giving hints about your likes and preferences instead of directly telling them you are gay after attending a crazy queer party or an inspiring queer workshop. Be calm and act smart.
If your identity is quite evident with your postures and gestures (if you are effeminate enough or masculine enough which remains moderately different compared to typical heterosexual behaviour) then you don't have to stress about it much. Always remember, your personality is more than your feminine or masculine behaviour and they are your parents, they must be observed those traits in you by now.
Speaking of it, don't think that your parents