Taking care

I think i don't know how to take care of another human being. Including those little ones in my class and also the senior ones at home. Nor do i know how to take care of my contemporaries. I don't seem to know how to take care of animals too.
Bought little fishes for my classroom last year to teach my kids. But somehow, they are seriously 'tortured' by me. My colleague cared more about my fishes than me. She brought filter from her home, teach me how to use it, and pops by to check the tank. CLassic: There was once, we had a 4-day holiday (including weekend) She was so worried for them that she actually climbed the school gate, rescued my fishes and brought them home so that they would be fed and taken care of during that period. She has such a kind heart! I felt so guilty for being a heartless owner... but somehow it didn't come naturally for me to think about them... Really bloody heartless.

Must I wait till I have my little own human being before knowing how to genuinely take care of one and shower him/her with unconditional love? Or perhaps HORROR- even if i have my own kiddy (quite unlikely... haah) I'll still be a selfish brat. A self-centred person who have to make a conscious effort to care.
Is the capacity to take care and love someone innate in us, or must it be learnt? The scary question for myself is however... CAN it be learnt?