Is he at all interested?

I'm (M) wondering if a coworker of mine (also M) could be interested. I'd say we consider each other friends, he's the person I'm closest to at my work place. I don't know if he could be bi-curious or interested in guys in any way. When we text he uses hearts and kissy emojis in a not joking way but idk how serious they can be. I'm the youngest of all our coworkers so we always joke about me being a child and him being old as fuck even though he's only 3 years older than me, so sometimes he calls me son and I call him dad or grandpa just to mess around. He's okay with it he does it as much as me. The topic of our sexualities never came up so he might think I'm straight and see this as a simple friendship. Could he be interested?