I've noticed that my main male seems to produce two to three cubs whenever I breed him to my girls, whereas if I breed those same lionesses to any other male they only produce one cub. I'm sure it's just good luck or chance, but it got me thinking. Here's my idea:

Male lions would have a fertility level, similarly to the way lionesses do, only it wouldn't affect mutations. Lion fertility would instead effect how many cubs the lioness he bred to produced. A lions fertility would be randomly assigned when they are created, to ensure that Low to Average fertility remains the most common and doesn't result in a large amount of god fertility lions. For the sake of those who have a dream lion but an undesirable fertility, items such as Tackweed, Chasteberry, and Buffalo scrotums can be used to temporarily raise the fertility level or cub production for the next breeding. Fertility results and rarity would work in this manner:

• God Fertility - Very Rare - Higher chance of having four cubs
• High Fertility - Rare - Guarantee of at least three cubs
• Average Fertility - Uncommon - Guarantee of at least two cubs
• Low Fertility - Common - Guarantee of at least one cub
• Infertile - Very Rare - Unable to produce cubs

Questions and Answers:

[Q. Imagine you've finally created your dream main male, high stats, special base, and ten markings, and then you find out that he has a low fertility. Not only would that make him less desirable, but it would make lions with high and/or god fertility much more desirable.]
[A. This is true, but only to an extent. You would know his fertility as soon as you check his profile, because it would be displayed in the same way it is for females. This could prevent you from going to the effort to make a dream male from a lion with low-average fertility. A male as described would still be more desirable than a lion that has low stats and an unattractive appearance anyways, because even if that lion has high and/or god fertility, three-four bad cubs aren't as valuable as one or two from the initially mentioned male. However, if fertility is such an issue, then you could always use breeding items which would override the lions original fertility level during his next breeding.]

[Q. Wouldn't this make it harder to sell male cubs that don't have high or god fertility?]
[A. It depends on how Lioden users sway. To some, fertility may not be very important and they would purchase a lion regardless of fertility due to the rarity of high and/or god lions. It would be very challenging to find a perfect male that also has a high/god fertility in any case.]

[Q. How would the sex changer item work in terms of fertility?]
[A. The same way it does now. When one changes a gender to that which they desire, it would reset their fertility to whatever would appropriately accommodate that gender.]

[Q. Wouldn't an infertile male defeat the purpose of having a main male?]
[A. For some, yes. This lion simply wouldn't become the main male. Some people however, might not even use their main male for breeding but instead for exploring and pvp battles.]