My humanoid aliens grow and age the same way as humans but it's a much slower process. It takes them 2 years to physically age and grow. If one is, let's say, 50 years old than their human equivalent age is 25 years old. It's easy to calculate their human age. Take whatever number divided by 2. I wonder how long the pregnancy should last (They produce offsprings the same way a humans). In humans, it's 9 months. If I were doubled it, would be 18 months but being pregnant development would be slower. I'm not sure if I want to go there. A 9-month pregnancy is already hard enough.
Here's how it would be:
Infant/Baby: 0-7 yrs (0-3.5 yrs)
Note: There's no toddler
Child: Under the age of puberty (a person is no longer considered a child when they hit puberty)
Note: There's no "teen" or "adolescent".
Adult: At and above the age of puberty
Elder: When hair starts graying
Puberty begins somewhere between 23 (11.5) and 26 (13) years old. There's no late or early puberty. Puberty lasts for (only) 3 years.
You are an adult when you start puberty.
You're are considered an elder when you're hair starts graying. It happens sometimes between 76-108 (38-54) years old. Life expectancy is between 160-200 (80-100).
Does the aging make sense and how long should the pregnancy be? (since they age slower)
Note: This is a very humanlike species (with a few anatomical, physiological, psychological, biological, and physical differences). In my universe (real life-based universe), my humanoid aliens are the only human-like species outside of Earth. They are cousins to Earth. Compared to humans, they are technologically and modernly behind.