How??
Naruto has Hagaromo's Chakra and Hinata has Hamura's.
When the two together it make's Kaguya.
So by Science definition, Bolt and Hima should have Kaguyas chakra unless it's an recessive trait.
Same for the ppl who ship Salt
Sarada inherits Sasuke's Hagaromo Yin chakra and Bolt get's Hagaromo's Yang
Steven gonna be a full fledged Hagaromo in the flesh
Hagoromo chakra is exclusive to Hagoromo only and Hamura chakra is exclusive to Hamura only. Combining them will not turn it into Kaguya's chakra. It will be a combination of HagoHamura chakra. New type of chakra and power will emerge.
People dont clearly understand what exactly Hago did in the past.
1. Hago clearly stated that he passed-down to Indra his eyes and chakra power while Ashura with his body power. And by combining his two sons chakra will lead to awakening of Rinnegan. It being set by Hago.
2. Kaguya never been said to passed-down any of her trait/specialty(like eyes power or body power) to Hagoromo and Hamura, just her Six Path chakra quantity.
Yes Rinnegan was/maybe a mutation eyes from Rinn Sharingan and Byakugan but combining Hago's chakra and Hamura's chakra wont gave anyone a Rinn Sharingan or Kaguya special KKM.
Only way to get Rinn Sharingan is from eating chakra fruit. Only way to get Kaguya level of KKM also by eating chakra fruit. Another way is by becoming JJ. It also involving the person with chakra fruit there(Kaguya).
There is no short cut like combining Naruto, Sasuke and Hinata's chakra. It bring nothing similar to Kaguya's chakra and level.
Even people that awaken Rinnegan after obtaining Hago's chakra from combining Indra and Ashura chakra still not on Hago's level without massive injection of Six Path chakra source/supply.