The concern that you have for your son is valid and on task. I do so hope that you realize that I can not tell you what to do; however, at the same time, I am not prohibited from providing strong suggestions to you!
What you are seeing is disturbing and is not considered a normal part of a Pre Kinder or Kindergarten child's normal sexual development. Though these tiny little ones do go through an exploratory phase of sexual development it is not even close to what you have described.
The "normal" or average 5 year old child might demonstrate that they are in this phase by a few or all of the following:
Why do mommies get babies in their tummy?
Why don't daddies get titties? (if this is a word they have heard while observing a cow nurse her baby - as an example)
If at a zoo or on the street this 5 year old child would see two animals copulating or mating---What are they doing...Why is he hurting her (some females squall)... Is her babies butt dirty? (When he sees a mother stimulating the urinary and colon muscles of her young)
These are but a few of the questions or comments that would be considered within the very normal range of the 5 year old child.
Gestures or behaviors that you night see this child engage in when playing with a peer or a doll follow:
With a doll... A little girl may kiss her on the cheek or forehead as she lays her down for a nap --- If this is what her parents do to her at bed or nap time.
With an apposite sex peer while playing house... A kiss on the cheek or lip (more of a peck) or a hug that is brief when they are playing mommy and daddy and the daddy character is leaving for or coming from work or the child character is leaving for or returning from school.
Also, if the children are playing mommy and daddy it is not uncommon to see them enter the bedroom and lay down together if each of them has 2 parents. Here is the kicker on this though... While these two children (coming from healthy environments) realize that mommies and daddies share a bedroom and have one bed in the room indicating to the children that they sleep together, these two little ones will lay dawn side by side, face, abdomen, thighs and toes pointing up and their arms are usually at their side... They have the bedroom part down pat in that mom and dad share one... They have the bed part down pat in that mom and dad share one... They have no idea of the sexual acts that take place between their parents...
On to your direct concern:
To be in the same room with his mother as she is receiving a bikini wax when a child is 2 years of age is one thing...(I would not suggest even this as it shows total disregard to developmental boundaries for the child) However, with the child being 5 years of age indicates to me that concern for sexual abuse is imminent. The 5 year old is curious and this is to much information for a parent to provide him with via means of observation. The second indicator is that the child is drawing detailed pictures mom's vagina and boobies according to you and this tells me that the child has observed his mother's breast's and vagina up close and this is how he is able to provide detail in his drawings.
The fact that the child reported to you that he puts his fingers in his butt hole because it feels good, tells me that there is high risk that he is in fact being sexually maltreated "raped" or that he is observing pornographic films or he is viewing his mother and a male paramour engaging in sexual activities.
Children are bright; however, unless they are exposed to a stimuli, they can not provide a reaction. A simple example is the child that has never eaten an orange... To look at the piece of fruit is pleasing... To see the piece of fruit being peeled is fascinating as the child finds that there is a secret "something new" under the skin of the orange, ... It is not until the child bites into one of the orange segments (stimuli) that he will provide a reaction, a frown on his face indicating a dislike for the fruit or that the fruit is tart... or a smile and a request for another piece indicating that he received pleasure when eating the orange.
I am going to suggest that you not allow the child to return to his mother until you have contacted the division of Child Services in your area and allow them to further investigate this potential risk. I am confident that they will inform you or assist you in gaining temporary custody of your child to ensure his safety until they have completed their work.
As I see it, your child is 5 years old. You must be his voice or he may never be heard...
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