Hi,
Depending on his color mutation, you may be able to tell after this molt. With some mutations, you have to do a DNA test.
Are you wanting to breed? You will lose Buddy as a pet if you get him a mate or companion and put them in the same cage. Once a bird has a bonded mate or same sex companion, they tend to lose interest in human companionship and often become aggressive and start to bite. If you are wanting to breed, and you are willing to lose your bird as a pet, then you need to wait until Buddy is at least 2 years old, and the mate needs to be over 2 years old, too. Ideally, you should wait until cockatiels are 3 before you breed them, giving them time to fully mature and develop physically and emotionally. If you pair your birds up too early, they tend to develop bad breeding habits that can ruin them for being good breeders.
Thank you for asking Lafeber,
Brenda