also i'm not really going anywhere with this post but i think i'd characterise gareth as Just A Chill Guy. the only time we see him in the book, he's playing with neil who has a look of "patient suffering". so he definitely tries to bond with neil and neil probably finds him extra. neil seems to have inherited megan's strong will and lack of filter (and probably even howl's dramatics — "that's just playing with a person's feelings") so i think he'd have some beef with gareth over this, especially as a teenager.
i also think gareth is black since he and neil are described as "dark" and that megan married him against her parents' wishes. but she's also interested in fitting in and being Respectable and being a biracial family doesn't help with that, so she holds some resentment/anxiety over that. i do think they love each other and are a functional couple, but whether they fully understand each other is another question. i'm picturing gareth as easygoing and friendly, and his presence makes megan happy on good days and he likes her strong-willed personality, but he's not great at understanding the full extent of her emotional constipation.
howl doesn't seem to get along with gareth from the "warm, false smile". i gave them a single interaction in my fic where gareth tries to talk to howl and howl doesn't reciprocate. i think their relationship is just awkward. howl finds gareth too normal and boring and genuine and doesn't really know how to keep up, so he slithers out of interacting entirely. but fwiw i don't think gareth ever minded howl living with megan and freeloading on them, it's megan who had a problem with that because it reflected badly on her. gareth imo is nice enough and too chill to care.
as for mari i have absolutely no basis for thinking this, but i'm headcanonning she's closer to gareth than megan. if megan is the strict parent and gareth is the pushover the children respond to them differently. like i see neil finding gareth annoying at times and wanting space from him, i see mari finding him fun and easy to hang out with. mari inherited gareth's personality mayhaps?
(as for megan's relationship with the kids i think she's strict but also they're both close to her in the sense that she's a stay at home mom and spends a lot of time with them. i can't extrapolate much about mari since she's pretty young, but i'm sure neil absorbs a lot of megan's opinions from how he calls howl "no good". i want to think he has a close relationship with megan where he gets in trouble all the time but she's a softie deep down.)
.....this post wasn't going anywhere but it's a parry family headcanon post now ig
