He may be the parent whose kids you babysit and who texts you far too frequently. Getting connected with a married man, regardless of his position, is a perilous and complicated thing to do. It is not a suggested path since it may lead to a lot of uncertainty and problematic relationships, especially if you know his family. However, for some women there's no better option available so they attempt to marry their sons-in-law or daughters-in-law.
The first thing that comes to mind when thinking about marrying into another country's culture is prejudice. If you're not aware of how people feel about marriage in the country you're marrying into then you might be surprised by some of the reactions you receive. In many countries (especially Muslim nations) marrying within your faith is common because of prejudices against other religions. If someone is opposed to your marriage then they might try to sabotage it by telling others that you are both divorced or that you have children together.
There are also cultural differences between men and women that make each relationship difficult. For example, in many countries being married makes you equal property owners together; this means that if he wants to divorce her then he has the right to since she cannot leave him alone with these rights. In other words, if he decides he doesn't want to marry her then she has been left without a job or income. This isn't always the case but depending on the country there can be lots of legal complications with being married.
If you've met his wife and she is aware that you and her husband are messaging, then there is no problem. On the other hand, if you're flirting through text and you don't know for sure if your wife is alright with it, yeah, that's horrible. If he is married, perhaps he should ask his wife how she thinks about it. Then you can decide whether or not to continue the texting relationship.
Also remember that even though he is married, he is still a person with feelings, so don't text him too much or tell him too many personal things unless you are ready to be rejected.
And finally, don't do it anyway. No matter what kind of relationship you have with his wife, if you text this man and don't stop, eventually you will end up in trouble. Even if he says it's cool at first, soon he will want more from you than some friendly conversation, and when that happens, you'll need to consider changing your ways.
So in conclusion, yes, it is okay to text a married man as long as you aren't causing any problems for him or his wife. Otherwise, you might end up getting dumped!
When you date a married man, you will always be second best. His wife and family will take precedence. Remember, he's covering up his infidelity, so you won't be able to readily reach him, he won't be present for critical events, and you'll never be able to rely on him. This is not a good situation for you or your children.
If you really want to be involved with this man, you'll need to decide how much risk you're willing to take. Are you willing to wait until he decides he doesn't want the marriage anymore? Or would you like to be ready when he does decide to leave his wife? If you choose to act now, you'll need to be prepared to move fast if he changes his mind.
The safest option is to stay single forever. The more difficult option is to figure out how much risk you're willing to take.