*grips your shoulders* an eight year old is not gonna act like that. put the pen down. close the laptop. stop writing for a minute. volunteer at a daycare center for a week or smth. an eight year old is typically (unless they're purposely doing it, but at that point you'll be able to tell) not going to speak in one word sentences. that is a child with a possible developmental delay and should probably get an assessment done. that is a two year old with an MLU score of 2.0 who is struggling with their present possessive verbs. look up the average heights of an eight year old because i promise they're bigger than that.
if your six year old is still doing reduplicated babbling and it's not clearly an on purpose active play decision, then they should probably (re: REALLY) undergo evaluation because one of the first signs of a developmental delay is delayed speech. children begin speaking in two word utterances as young as 18 months old. three year olds on average can hold simple conversations with adults. four year olds absoLUTELy can.
i know it's super fun to write children as being dependent and clingy to their parent for your super fluffy found family child fic but that is not a six year old that is a worryingly large two year old with a mild speech delay. you don't have to be 1:1 accurate, god knows i'm not but please at least know that children on average are capable of holding simple conversations by the time they're 4, and are usually doing the baby talk stuff to be cute or as a play thing. which isn't a bad thing but if they're talking like that unironically and ALL the time, then there is likely a problem in their development.