I guess it depends on if you are a strong enough Christian (if at all). If you propose this to GOD and ask him for an answer he will send you a sign, if it is to go ahead with it, then DESPITE your faults or weaknesses it will work out in the end.
Everyone likes to twisted what "my brother's keeper" really means. It means if your blood brother dies, WITHOUT a child alive to inherit the property and name, you were legally and morally obligated to go into the widow and help her conceive. This is where Cain, (imho) was being a wisenheimer to GOD when he said:
And the LORD said unto Cain, Where is Abel thy brother? And he said, I know not: Am I my brother's keeper?
Besides being a liar (like his father Satan) Cain was saying I (being from the seed of Satan) have no legal or moral interest in Abel because he is of a different father (blood line) then me.
Contrast this to what Jesus said:
Luke 10:29 (the good Samaritan story)
But he, willing to justify himself, said unto Jesus, And who is my neighbour?
What was Jesus's ultimate response?
37 And he said, He that shewed mercy on him. Then said Jesus unto him, Go, and do thou likewise.
Then Mark 12:31
And the second is like, namely this, Thou shalt love thy neighbour as thyself. There is none other commandment greater than these.
Then if the person was not too bright, what did Jesus say again?
Luke 10:27 And he answering said, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy strength, and with all thy mind; and thy neighbour as thyself.
> Thou shalt love thy neighbour as thyself.
If you were these kids, what would you want your "uncle" to do?
Watch the video by Everlast (not that I am a big a fan of the group with the foul language ) "Long at All"? with the homeless man riding the bike.
Legally you are not your brother's keeper to these kids. The question is how much do you love your wife and how much love will you show her and how much mercy will you show these children?
Could they be like the kid that strangled his mother to death in Florida over bad grades? Or the one that killed his grandparent the same week over a video game, absolutely! BUT, GOD is a shield against evil and if you do something GOD approves of then not even the likes of Satan, Soros, or Obama can stop you.
When you reject these children, remember in your old age, they will be running the country, not you.
If it was me, here is what I would do. I would get the three kids, tell them if you want to NOT live in foster care, here are the rules:
#1 You never raise a hand or voice to my wife. You do what she says, like my own children. If you have an issue, feel free to yell or hit me, just know you are getting it back in like manner if you tick me off too much. I have 50+ years of being an arse and get in some practice in my spare time on Pirate4x4. :-D
#2 I am legally adopting you and you are getting my last name. Until you are 18 -AND- out of my house and on your own, you are not to see these people at all (mother and/or father). GOD gave you to them to take care and they cared more about themselves, then you, You will be the thing I think of when I get up in the morning and before I go to bed. You will be more precious to me then gold.
#3 You are doing chores and getting part time jobs to help carry your own weight and build character. I certainly will be working more to support you when I should be thinking about retiring and storing away gold.
#4 Tell the parents (aka egg and sperm donors) in front of the kids (except maybe the 4 year old) You adults have two choices.
Choice #1 Your kids can be legally adopted by me and become my kids and live a decent life in a household where they will be loved. They can inherit what I have equally with my own flesh and blood when I grow old and die. Even if it is only $1000 each, it is more then you have now to give them. When they are 18 AND out of my house, they are then free to contact you, move in with you, or totally ignore you. Otherwise you have a restraining order not to be within the state of OK until that time. As for the choice of contact after 18 years of age, it is up to them though they will still be MY kids.
I suggest you use the time over the coming years to build a life for yourself where you can at least consider inviting them over to your own house for a vacation once they turn 18.
Choice #2 You keep on doing the wonderful job of providing for your kids as you are now, that GOD had entrusted to your care. I wash my hands of the matter. Though you all are welcome at family gatherings as in-laws.
"Without love you got nothing."