In principal... nothing. Occasional gifts are OK.... This does not extend to buying the brothers a jeepney or tricycle and then being rolled over for the maintenance and new tires etc...
Your girl will come under family pressure to deliver the goods on a monthly basis. Remember that most Filipino families will look upon you as sort of winning the jackpot.....
Help only in matters of true emergency sickness etc; and do this by directly paying for hospital/doctor/medication expenses...
Keep in mind that people in the Philippines can die of medical problems that we in Europe would never consider life threatening....
I remember vividly seeing one of our neighbours family financially ruined by the mother contracting kidney disease which required regular dialysis. She died after about 3 years of treatment. The children’s inheritance being consumed by medical expenses..
bystander