Crypton Vocaloids do not have officially established relationships. Anything not given by the company is considered Fanon. So no, Kaito and Miku are not related.
Just some notes in regards to this question;
- Kaito is a voicebank library for the original Vocaloid engine while Hatsune Miku is Vocaloid 2.
- Miku is for the CV series, her number is CV01. Kaito does not have a number and is not a member of the CV series
- He is Meiko's counterpart in the Vocaloid series of voicebanks of which there are only 2 of.