You're a good kid but you're still thinking in absolutes like an idealist. I get thet your parents are ideologically backwards, I get that they're indulging in exploitation, but if I'm reading it right they aren't professional landlords or anything. They're still labourers and have one extra flat they're renting out. That's very near the bare minimum they need to provide comfortable lives to themselves and their children.
Today it's near unavoidable to have some money and not engage in some petit bourgeois behaviour, to an extent that doesn't necessarily make someone petit bourgeois. Keeping your money in a rented flat or shares in companies (as it would be in those pension funds) is participating in exploitation, but what are your alternatives? Keep it in the bank and the interest they'll give you is less than inflation. Buy a flat and keep it empty, now you're participating in the housing market the same way as landlords refusing to lower the rent. I suppose you could buy gold and hoard it somewhere.
Your parents aren't bad people for participating in the society they live in and neither are you for "profiting" off that. As for their ideological inclinations, people don't leave liberalism by being convinced. They see the conreadictions of capitalism and have someone explain what it is they saw and how it fits into the bigger picture. Watch out for that and you may make comrades out of them yet.