I love you, and I wish I could give you my address, but our parents harassed me about having children constantly by showing up at my home. It really was very stressful, I don't want to deal with this anymore, and for now that means I'm not giving my address to people close to them. This sadly also means you. I'm sorry, I want to invite you to my home, but right I don't want to risk our parent knowing where I live. I hope to find another solution soon.
I would say something like that to him (you might change something based on the details of your situation). Here are the key parts I'm trying to convey :
Reassure him. Tell him you love and appreciate him, and that under normal circumstances you would have loved to give him your address.
Focus on the real problem, your parents. Again, this reassures him that he is not the issue here. Also, if he isn't aware how pushy your parents have been or how it made you feel, share that with him if you're comfortable. The more he understands where you're coming from, the less likely he'll take this personally.
Try to not mention his specific shortcomings. Instead of saying that you don't specifically trust him, say that you won't give away your address to people who have a high chance to give it to your parents. This again shifts the focus from him to your parents : it's not about him not able to keep a secret, but about your fear of your parents finding out. That's why you have a blanket rule.
This of course only works if you're not sharing your address with other people. If he is the only one you're hiding your address from, try again to shift the issue to your parents : you know how difficult it is to keep a secret from them, how persistent they can be, and you don't want to put him in that position. If he still pushes at that point, only then remind him of the other times he did spill secrets, and that this in addition to everything else means you're not going to share your address.
Say it's temporary. This should make it sting less and make him more patient, knowing that you plan on being able to share your address with him. Again, only say this if true, but I don't think this is a viable long-term solution. When you're ready, I'd advice talking to friends or a psychologist to figure out another way to establish healthy boundaries with your parents (like refusing to let them into your home unannounced).
EDIT : I forgot we have to add personal context now. I don't have a specific example in my life about this kind of issue that comes to mind right now. In general, when I have an issue which is a mix of a specific someone and a situation, if that specific someone has an involuntary impact on that situation I try to reassure them and to keep the focus on the situation. This keeps from things getting personal and avoids unnecessary hurt feelings. Often people still get a bit hurt (you're still at the implying that person did something wrong) but if they understand where you're coming from and don't resent them, it doesn't affect our relationship and once the situation is resolved all is forgotten.
