First, thanks everyone for your advice. Some posters have put a lot of effort into long detailed replies. I appreciate it greatly.
Second, I am sorry that I have not been able to reply frequently. Due to the sensitive nature, I have to wait until I am alone, to post.
To answer some of your questions
MIL got a redundancy package in 2003. Started a lifestyle she couldn't afford, and now has credit card and loans debts totaling $15,000. Most of her income goes to pay off her debts. I try not to be hypocritical, (upset she saw my payslip but demanding to know her income) but I gather that she was means tested when she still had half her redundancy package, which meant she was not getting a full dole, but she managed to bring part of her pension forward. So she gets about €1,000 a month. She is going to try and get means tested again.
BIL gets jobseekers allowance/benefit of about 100 a week. FIL is not really in the picture. He does not live with MIL. Doesn't pay child support because BIL is over 18.
In the last few months BIL has tried looking for jobs but he dosent have his leaving cert and he is competing with college graduates for the simple jobs. Maybe I can convince him to join the army
My parents bring in about $1,200 per month from a private pension. They get most things they are entitled to. My father was a factory worker.
Before we married my net pay was 6,000 and wife was 2,000. Please do not think I am a saint or unusually generous, and willy nilly hand out money, but at the time, giving 10% (600) to my parents, seemed immaterial. A small amount to me but a great deal to them. As I said, I could not enjoy myself knowing they were scrimping. I didn't want to be middle class while they were still lower class. Maybe since the recession, I have felt fortunate to still have a job and a moral obligation to share with those less fortunate than myself.
Also before we married, wife was staying with MIL and contributing to the daily expenses in that household. When we married, she left their house and that left a hole in their budget. I tried to be open and fair. We were bringing home 8,000. Giving 600 to her family and 600 to mine seemed fair and the right thing to do.
I will look into Deed of Covenant and Gift tax. I was also thinking of buying MIL's house from MIL and stating that these money's should be put towards the purchase price. But at the moment, I don't want to create any other liabilities e.g stamp duty. Maybe we can agree that rather than sell it to me, she leaves it to my son in her will. I will look into it.
From the replies I now think that this is probably more a relationship issue than a money issue and the recession has made normal people act crazy. Another attempt at a sane discussion with wife seems to be the best step, after all, we did marry. And there was something in those vows about "in sickness and in health, through rich and through poor, till death do we part"
I deeply thank you all for your replies. You are the best. I wish I had the time to send you each a private thank you pm.