This is a super sensitive and personal decision to make.
If you already believe that you will be giving/spending money in the future to take care of your family, then certainly plan for additional funds per year to adjust for that.
You will also want to take into consideration some "boundaries" that you can agree to in advance. For instance, we are still in our late 20s, so MIL is nowhere near retirement age, but she is already regularly in dire straits. She regularly has cable tv, buys dollar store junk, smokes, and on and off refuses to have a roommate or share an apartment with family. Thankfullly, we are not local to her, so any requests or "hints" have to be communicated via phone calls.
We have, in the past, agreed to spend 100 here or 150 there to keep her electric on or to catch her up on health insurance premiums. She complained about the costs of prescriptions once, we did the research long distance and arranged a discount card for her that she qualified for and found a pharmacy that would let us pay over the phone for the most important of the meds if she ever couldn't get it (heart medication). She took the discount card, but so far we haven't had to pay for the perscription. I still don't know if what she actually wanted was cash (perhaps she just didn't want to ask directly for it), or if she actually needed the discounts and can now afford the meds. We almost never send her cash...we call up the company she owes and work something out if at all possible. We have also told her no if she has made requests more than once or twice a year...so our costs so far have been relatively negligible. DH's brother has helped a few times, but generally they speak to one another about it beforehand.
Recently, MIL asked for a hefty amount in comparison to past requests. She was moving in with her mother to share living costs and needed 1000.00 to settle with some bills she had gotten behind on with the other apartment and utilities. We talked to her for a bit, found out she was giving up her cell phone plan for a prepaid, letting the rent to own furniture get picked up, and would be helping her mother with bills. We said we could help if she did the following. We wanted her to sign up to be a member of the local community center, which provides free budgeting classes and free or nearly free weekly activities like bingo, art and pottery classes, exercise classes for a buck or two a class, ect. Much of her issues are emotional...and she seldom leaves the house unless she is working or blowing her money, she has no community. We also told her that if we gifted the 1000.00, it would be last in a while. She spoke with her mom about it, who encouraged her to do it because our desire was simply to be happier, healthier, and to have relationships outside of her family (who she milks to death). Instead she called us back and turned down the funds.....