I mean we've already seen Helios admit his attraction towards Hestia and his jealousy towards Cael for having such an amazing wife, even promising to himself that he wouldn't repeat what happened before (them competing for a lover) so Helios is definitely attracted to Hestia but it's completely one sided.
On the other hand Hestia feels nothing but anger, annoyance and disgust towards Helios and Diana. She admits they're good looking but that's it.
Yeah now that you say it it has been a while since I've read the story so I kinda forgot about Helios develoment in the last chapters. I remember finding it forced, I really enjoyed it most when he didn't have such feelings
Also it may be an unpopular opinion but I don't think he has any real romantic feeling for her, a bit of attraction as you say but that's all.
it's quite ambiguous but to me he is jealous that his friend has a capable wife while he has to take care of all the troubles that Diana caused, basically he wishes for a supportive wife that he associates with Hestia but I don't think he really likes her as a person
I love that there is not 1% romantic tension between them they just fight for the sake of annoying the other (Hestia especially) I hope it will stay that way this story doesn't need a 2nd ml especially considering Helios and Cael past issues