Is it normal to be two different people?

Family dude! this all is gonna go away and family is all you gonna have left..
How long will you stay taking drugs and having sex before you die of an overdose or get in prison.
how long will it take you to find the one who will accept you with your drug addiction.. Drugs will ruin you, take it from an old addict!

If I'm not me who am I and if I am somebody else how come I look so much like me?

100 % agree with "babyscarer", although your user name freaks me out a bit...lol. Choose family...they will always love us through all the bs we get into over our lives, they will kick us when were are already down, be there to lift our dumbasses back up, but surely don't have to like choices we've made. I used to get so pissed off when I was younger and they'd say, "hunny, we have rules and enforce them, because we love you". I only truly understood this when I moved out at 17 and REALLY get it now that I'm 27 with a child of my own. Choosing between friends vs family shouldn't be a hard choice when the friends you have are letting or causing the trouble you're in. Once you grow up a bit more only to figure out who " you are", will you understand why they are making you choose. Remember, even if you make the wrong choice for now, your family will still be there, but gaining back respect for some mistakes can take longer than most of those "friends" will even be around in the end.

Yea it is normal. The truth of the matter is that you are insecure and you are trying to find reassurance through one of the 'personas' you are putting on (most likely the ones to your friends).
It is normally especially at a teenage age to be insecure andact different around your friends but it is not healthy. Please don't think just because it is normal that it is ok because it isn't.

A perfect hobby for you. That is poetry. Poetry is about imagery, not just maki g words rhyme. Often poets claim that there's two of them. The one people sees and the more hidden one. People like yourself make excellent poets. So, try putting a little pen to paper and see what happens

If you have to pick one, choose your family, drugs will get you put away, sex can get you aids or some STDs. Family is always there for you, you can always be around them and spend time with them and there's nothing wrong with it at all.

BTW I am multiple people, I go by Joshua(real name) or mark, Maxwell, Damien, Jonny, Derek, and Mike, those names even have last names too. Its a part of my personality disorder

family.........DUH

It seems like you're the chameleon type. You haven't really developed your own identity (yet), so you're always behaving like the people around you. Watch the Woody Allen movie "Zelig", it's an interesting take on this.
The hard way of solving this would be figuring out who you really want to be, deciding on your morals and always acting based on them, but this could take from months to forever.
The easier way is to change friends - if you get some better friends, you will be better yourself. I'm assuming this is the part of your life/personality you'd prefer to change, because obviously, drugs and prison are unfavorable things to be involved with. Also, you can't change your family.

Hm, to choose between drugs and sex, or your family. That IS a tough choice, I can see why you're confused.

.................really?

Can you be more specific, please? As for choice one to keep, I would go for the third option - go find a new hobby and friends. Friends come and go, but family stay. Always.