I am the father to 3 healthy boys, aged 12, 14 + 15. 
 
I was divorced from their mother 8 years ago. My 2 oldest sons live with me, and they always have. My youngest son, lives with their mother. 
 
I am an Englishman living in Denmark, and for reasons that need not be gone into here, that is the decision that was made. My ex- wife moved back to "our" town about 2 years ago with a guy she was living with, and consequently married, last year. 
 
Under Danish law, I get to see my youngest son every 2nd weekend, alternate holidays and special ocassions like birthdays, and so on. 
 
About 18 months ago, I approached my ex and suggested to her that our 2 oldest boys lived with her ever 2nd week for 5 days. This way, they could develop their relationship with her, her husband and their younger brother. Plus, my 2 oldest boys have breakfast most mornings at their mother´´s house, so all 3 boys can go to school together. 
I admit - I have regretted it many times, but only because of selfish reasons ...... (these thoughts I have "always kept to myself") 
Now my youngest son is 12½ years old - (he lives 1 mile from our house), my ex says I cannot see my youngest son more than I do as it would not be good for him, as he is better off with her! 
Of course, I could contest her and be proven right on this issue........... I just know my sons know Dad is always there for them. All 3 of them. 
 
 
Anyway - that is one story about "shared children"...... another is :- I met a woman - online - that was the woman of my dreams. We chatted, wrote, mailed and called each other for hours at a time. 
She lived in the USA ... she visited me and my boys here. It was great . 
Earlier this year, I visited her in her home. 
 
The downside is / was, she has a shared child with her ex. Under US law there is a "60 mile" rule for enstraged parents. My American g/f cannot move outside of the US, (understandable), with her daughter. So, a year later - it is over.  
Do divorced Americans only re-marry Americans? 
 
No matter what - Kids come first.