My step grandpa passed, and I want a tattoo in latin that says, "Blood isn't always thicker than water." I would greatly appreciate it if someone translates this.
The proverb "blood is thicker than water" originated in German, so all Latin versions are translations from that. The one I've seen most often is:
Sangvis aqvā densior est.
Densior is quite literally "thicker". You could also use spissior "denser" or dūrābilior "harder to break"; either of those can be substituted in freely.
Another Latin proverb is "no man is always wise":
Nemō mortālium omnibus hōrīs sapit.
(Literally, "nobody among the mortals is wise at every point in time".)
Combining the phrasing from those two would give:
Sangvis nōn omnibus hōrīs qvam aqvā densior est.
I added the qvam to make it clear which ablative goes where, since there are two in a row. But you can freely drop the qvam and est without affecting the meaning.