I was in a long distance relationship (across the globe) for 4 1/2 years. We met twice, once in each country. When we got married we had spent a total of 35 days together. We've been married now for 7 years! Here's some points about it all..
1. The person without the kids has to move to the country of the person with the kids. If they are minors you can forget about immigrating with them anyway. If not, well.. the person with the kids is going to be deeply pained eventually to be living so far away from their kids, eventual grandkids etc.. in the "whose family is easier to leave" stakes the kids always win for being the ones you don't leave.
2. You need a plan and you need a target time to accomplish it. It's SO MUCH WORK (I cannot emphasize this enough) moving countries. Once you have decided you are going for it arm yourself with all immigration information, job prospects etc.. and start planning.
3. For the person moving there will be great sacrifices, many completely unforseen. The other person must know this and plan for this. Do not make this move without trips back home being in your budget. I have known many people just pining away because they don't ever get back to their country of origin because it seems like a selfish expenditure when they have family needs in their new country.. for some people this is a slow death.
Yes it is possible, and easier the younger you are. Don't put it off another 10 years, it will be too exhausting to even think about. IMO it's worth risking instability for a good relationship.. you can always pull yourself up and get back on your feet in careers etc.. but you can't always find someone you really care about like that.
The language is a difficult point, though not as hard as one not being able to imagine going to the others country. Really someone is going to have to sacrifice more in this scenario and not resent it, it's just the way the math falls.
Oh and let me add this very unromantic warning:
To the person moving countries, think VERY HARD before you have children in this relationship. Once you have those kids you will never be able to move back to your country of origin with them if the relationship fails. You are stuck there forever because of course the other parent will never give you permission to leave. No one ever thinks about this but it is worth delaying having children just to see how the relationship weathers being together full time.