You can attempt to assert yourself when you feel he is condescending. For example, he is rude to you if you come over, let him know that you are an adult and if he continues to be belligerent, you're going to need to leave. Or if he gives unsolicited advice, assure him that you can handle the situation, or if things go wrong you'll deal with whatever happens. The thing with this is that people like this is that you have to address the situation specifically as it happens, every time (or nearly every time) it happens. Having one big talk with him probably won't help. If you let things fester over time and then blow up at him once, he won't "get" it. It's constant reinforcement. As stated above, this may never stop so you may need to distance yourself from him.