Headcanons for dev and wanda plus some for cosmo but mostly wanda lol
Part of wanda's attachment and smothering of dev has to do with their past relationship with timmy and how they had to leave him. Leaving a godkid is hard enough but timmy like dev was heavily neglected by his parents.
When they finally had to let him go wanda not only missed him like crazy but felt so guilty for leaving the kid on his own when clearly the world wasn't looking out for him the way they were. So out of anxiety and that fear she's very attentive with dev. She would've been like that anyway though because the mistreated and neglected kids are the ones wanda tends to baby and spoil the most.
Between the two of them cosmo is the more level headed and calm one. Not a buzz kill exactly but he helps keep wanda and dev afloat and from completely going off the rails. I like to think their vacation helped him mellow out while for wanda she was still plagued with anxiety and fear for the kid they last left behind. Cosmo gives dev stability and always offers wise advice. As well as his support overall.
Wanda will let him ask for any out there or even dangerous wish as long as they're with him to protect him and to provide him with the right protection. Helmet, knee pads and elbow pads etc.
She has several nicknames for him my baby, our baby, my little man, sweetie, honey, sweetheart and little dev when she's really babying him.
Him getting most of his food from wishes from wanda cause while she didn't cook it she used her wand so that makes it feel like it was made with love.
She'll just hum or sing as she brushes his hair when she wants him to look his best for events like school picture day and his dad's social stuff and him just finding her voice very comforting and soothing.
As a cover and for them to always have the excuse to be around him cosmo and wanda in their human disguise are hired as his nannies/assistants.
If his behavior gets really bratty and bad wanda will not be happy and I think that in itself is a punishment for him. I feel like he will apologize so fast if his mom is upset with him even if he doesn't know what he did.
Cosmo basically fills the role of his dad so everything he's ever wanted to do with his dad but he seems too busy for he does with cosmo instead.
Cosmo calls him all the son nicknames. Champ, sport, little dude and of course son.
When not in disguise as his nannies they shape shift acting as his new loyal dogs.
Once they makeup after him pulling away at the revelation that they're supposed to go away forever once he grows up him and wanda come up with a plan to either wish he's a kid for like fifty years like timmy did or simply act like they've gone away forever but in secret they stay with him.
I think wanda teaches him a lot of life lesson when it comes to social stuff. Like how to treat your loved ones and how to maintain friendships since he is prone to pushing others away and always having his way in certain situations.