1. What would I get them?
My brothers are teenagers... they wont be super happy to get a mug or keychain. My one brother loves coca cola stuff, but nothing is special here.
2. Here is the big thing. When I came to europe, I brought my own credit card. Because my card doesnt have a chip, it doesnt work at any of the stores (even with the pin). So right now, I am using my parents credit card. It seems weird to spend their money on gifts they may hate.
When you go to Barcelona, pls bear in mind that we are Catalans there and not Spanish, so pls refrain from buying fake Spanish souvenirs like flamenco dolls, sangria bottles or bullfight souvenirs (especially because bullfight is banned in Barcelona and whole Catalonia).
Regarding your general question, most typical souvenirs from touristic places are useless but you can always find objects which are worthwhile in normal shops, like books with old photos of that city, etc,
If you are away for a couple of weeks, do not bother. If you happen to find something that is right for the person buy it, with or better without a name tag for the location you are.
But if you are away for months or even a year you should buy some small items at least.
You use your parents credit card but I expect you will pay the bill for the card, so it will be your own money.
Select carefully, maybe something neutral like a calendar or a book about one of the places you visit/have visited.
A tour guide in Spain, as it happens, told me the way to do this is to have 3 categories of gifts. The first is the gifts for yourself that you bring back. These are the very nicest of gifts.
Then family and friends are next, so these gifts are cheaper, but not too cheap.
Then for work acquaintances and other friends. So in the airport, use your change, the coins only, and buy a bunch of key chains since no one will really expect you to go out of your way to shop for them.
A souvenir (French) is a reminder of a place you have been. They have not been there. NO
Buy a box of Anthon Berg chocolate in the gold box. They cost between 50-90 dkk depending on if you can get them on sale.
I think you should bring something back for your family. Even though your brothers may not like the present (they probably will because it's foreign and different to them) they will know you thought of them will you were gone and you can always pay your parents back.
