"Is he coming along?"
Translation:Komt hij mee?
Mee is the form met (with) becomes when it combines with a verb. Meekomen = to come with, also meebrengen = to bring with, or meespelen = to play with, or meedansen = to dance with. There are a number of verbs like this in Dutch. Met and mee can sometimes appear in the same sentence: Kom je met ons mee? = Are you coming along with us? The mee belongs to komen (meekomen), and the met goes with ons (met ons).