Re: Wife won't share expenses as a unit.
Like others have been saying, the fact that 50% of your income goes directly to your parents says something about your priorities. I'm VERY familiar with Asian families and traditions like this, but if your wife is from a different background, she will not understand. In her mind, it's why not 50% into a retirement fund, savings for your kids to go to college, or into a mortgage for a house that you can actually live in? Especially when all of the money you're pouring into rent currently is not an investment. You say that the house is going to be a good investment, and it probably will be, but it's hard to estimate the pattern of the real estate markets, and if it looks like the value will drop, it's not exactly like you can sell the house like you would sell a stock... And it's not like you can kick your elderly parents out of the house that they bought... And it's not like you can do all of this easily from another country... etc. What country is the house located? I just happen to know that China has a massive housing bubble right now, and that would affect my advice (I would be MUCH harsher towards you if this were the case). I do understand though that the "good investment" part of this is just an added bonus to taking care of your parents. But what will happen if they become ill or need assisted living or medical care? Will you be paying for this too? Unfortunately you are in a bind, because you can't abandon your parents, but you might not be able to afford all of these other things on your current income (I don't know anything about your financial situation, but it's just more to think about). In this case, you might HAVE to sacrifice the house in order to pay for immediate needs like medical emergencies.
Your wife is probably saying that they're "her" kids because she feels that she is the only one thinking about their financial futures, and she is the only one saving up money for them. In her opinion, you are not supporting your family, and by American standards, you're not living up to the image of the husband/father as provider. You claim that she is being selfish, but I think she is probably scared that if you two share money, then you will take more of "her" money to give to your parents, rather than keeping it for your kids, or for yourselves in retirement, so that your kids don't have to buy you a house or move nearby to take care of you when you get old!
I think that you both need to have a serious discussion about your finances--you can explain why you feel disheartened and unappreciated, and she can explain why she is so uncomfortable with you sending so much money to your parents. Unfortunately you have married into a different family, and maybe a different culture, and that necessitates some sacrifices all around. Your wife needs to compromise with you about how she hoards her money, and YOU need to compromise with her about how you are allocating your money. You might also consider speaking honestly with your parents about this--not to frighten them or cut them off, but to explain the situation. As it stands now, you're placing your parents above your wife and children, and I think that your wife is totally justified in being upset with this. She is NOT justified in belittling your choices or expecting you to pay for everything though. Just talk with her and maybe consider a different budget plan, refinancing the mortgage, or even getting a new mortgage with a longer time span but a smaller monthly payment.