They are opposite gender, adults, and they're relationships are both "[SIZE=14pt]partner"(full hearts). How can they start a new generation? I keep connecting and the female doesnt leave an egg. [/SIZE]
You must wait till each adult reaches 48 hours (2 days or Tama-years) of adulthood. Then, when you connect them, they will initiate the mating process.
If that doesn't work, wait till your Tamas are 6/7/8 (3 days after evolution from teen to adult, and the matchmaker shall come and offer you a partner. If you accept, you will have a baby.