The first of this threesome is the last to arrive, the other two are twins, merely 15. Once brought together they imprison many, and display their captives for the entertainment of the money holders.

(credit to u/SlumlordRising)

I might come through your window,

And I'm often at the bar.

Sometimes I'm used to send your kids

To die in lands afar.

(credit to: u/01010110_)

I fly out of the diamond

And, quite unplanned,

Into a hand

Or a stand.

What am I?

(Credit to u/Contene)

I will give it a try:

This belongs to you, but everyone else uses it. What is it?

Address

Name sounds much more likely, good answer.

Sorry it took so long to reply. Both are great answers, but name is what I was thinking of.

Silky and soft we are, perfuming your lives.

Take us to your love,

but beware of our knives.

(credit to theimbecile1134)

I am eating with a B

I am beating with a C

You will never show me to your spouse

And I never leave my house

What am I?

(credit to /the_dyl_pickle/)

Enter through one, exit through three. Once you succeed I am on thee. What am I?

(credit to Epacnoss)