Can you create a spark or does it have to be natural, and is it essential?

TLDR; old friend (13 years) came back into my life confessing he still had feelings despite not living together for 4 years, when he first confessed feelings I didn’t feel a spark so I said no, but we are older now and I’m unsure if it’s something you can grow towards as we are great together on paper

The TLDR sums it up, we lived together for 8 years, met in uni, travelled together across America and lived together with no issue, really it’s weird we weren’t a couple! All our family and friends wanted us to be together but at the time I wasn’t ready/was seeking a spark or was just naive I don’t know. Anyway cut to now, 13 years into knowing each other and we met up and chatted, went for a walk etc. and at some point he confessed he still had feelings and still thought about me. I could see a life with him, but I’m still a bit caught up in the friend zone and not seeing him that way. Has anyone been in the same place and got past it, or should I trust my apprehension? As I said we are great as companions. And he is good looking I just can’t get past the barrier.