I don't think you know what it means for an unbelieving spouse and/or children to be sanctified.
It means the believing spouse does not have to separate himself from his unbelieving family
like he has to other unbelievers.
God has
declared them clean for contact by the believing spouse so that he won't become unclean by contact with them
as he would with other unbelievers.
The problem with your argument is there is no such thing as God sanctifying other unbelievers in this way like he does for unbelieving family members. This sanctified unbeliever that you insist Hebrews 29 is talking about
doesn't exist. We are told to cast out those unclean people from the church. They are unclean, not made clean as you insist:
14Do not be yoked together with unbelievers.
17“Come out from them and be separate, says the Lord. Touch no unclean thing, and I will receive you.”
2 Corinthians 6:14,17
See? God doesn't make them clean (sanctify them). He tells us to separate ourselves from unclean unbelievers. The sanctified unbeliever you say Hebrews 10:29 is talking about doesn't exist. You're trying to apply the exception to the passage (unbelieving spouses and children) and it don't fit.