Generations
Generations were introduced as a way of keeping track of how many times the Tamagotchi has married and produced offspring. Generations are counted on the second screen of the TMP icon. This counter begins at 1 in the First Generation, and advanced by 1 each time the adults have children and leave.
Breeding
The Breeding (γγͺ-γ) icon is the 9th icon, and allows the two units to connect and produce babies. This icon can only be used once the Tamagotchi has reached the adult stage and has aged at least one day. When it's ready to marry, it will dance back and forth across the screen with music playing. From there, the user must interlock the two press and press the B button on both to begin the connection. If the connection is successful, the two units will beep again, and the word "OK" will appear beside them. Pressing the B button one more time will begin the breeding animation.
The two units must remain connected throughout the breeding process. The two babies born will always be the same, and which species of baby is born is determined by what its parents were. Once the animation is complete and the baby has appeared on both units, it is safe to disconnect them.
Sutebotchi and Tsuketchi are the only adults who are incapable of breeding. In addition, Ojitchi and Otokitchi, the two senior characters, cannot breed.
The parents will feed the babies whenever they themselves get fed, but it will be up to the user to clean the Poo and cure their Sickness. While the parents are around, the babies will get sick 2-3 times a day. After at least two full days have elapsed, the parents will disappear shortly after midnight and the next generation will properly begin.
TMP - Tamagotchi Power explanation
The TMP (TaMagotchi Power) Icon is located as the 8th icon, and appears as a smiling face wearing a crown. It tells which TMP rank the character is in and what generation it has grown to. When two characters of the same TMP breed, the resulting babies will be of the next TMP. If two characters of different TMP breed, the babies will have the TMP of the parent with the lowest TMP.
Baby and Child stage characters are universal between the two units, while Teen, Adult, and Senior stage characters are different. Characters are divided into four Tamagotchi Power (TMP) groups. Marrying two adults of the same TMP will result in a baby of the next TMP level. If one adult has a lower TMP, the babies will be of either parent's TMP (or, in the case of TMP2, the baby of that adult's lineage). Severe neglect during the child or teen stage may result in the next evolution being of a lower TMP.