They showed you kindness, perhaps in a way you'd never seen before, perhaps in a way you can never repay. But you're trying; in exchange, you're offering your loyalty, for how much or how little that's worth. For them, you'd do anything: you'd fight, you'd protect, you'd be their right hand or their biggest advocate, if they needed it and you can offer it. As long as you get to stay by their side, it doesn't matter.
So, you certainly don't have to worry about your bond surpassing what you have now or becoming romantic, do you? That will just get in your way of being there for them. Since you've only got their best interest at heart, it won't bother you if someone else were to pursue them...
As long as you get to stay by their side. As long as you get to fight for them. As long as they need you.