I would not worry about it. He is still really young and will catch on when he is ready. It is just like walking. Some children walk at 6 months, others after a year old, nut they do eventually walk.
I would suggest you first work on building up his fine motor skills. Since boys seem to mostly be active and use their gross motor skills, running, jumping climbing. that is their strength at this age.
Since you live where there are going to be times he is inside for longer periods of time, be prepared to work on some therapies to build up the fine motor skills.
You will need some small cars, like hot wheels cars.
Colors or markers large roll of plain paper, even cheap gift wrap with a solid color on the back will work. and playdo. Do NOT call it therapy, just treat it as play time.
While sitting at a table, have him roll out as many balls of clay as possible. Marble size is the goal. Show him how to roll them with only his thumb and pointer finger. use each hand.
Have him line them up. in a straight line. Then using only his pointer finger have him mash each one.
Have him roll little balls again, and line them up again. This time only have him use is thumb to mash them..
If he is up to it roll out the balls line them up and this time, you tell him you are going to call out Finger! Thumb.. and he needs to flatten the balls using the digits you have called out. ""finger, Thumb, finger, finger, thumb, finger, thumb, thumb, thumb.. You get the idea.
Roll out the sheet of gift wrap paper and have him draw a long line in Blue (you decide colors) them have him draw a big circle in red..
These shapes can cross over each other. Do at least 3 different colors in 3 different shapes. Make long lines and big shapes.
Then have him take a small toy car and "drive the car" only using his pointer finger down the blue line. Then the red, then the third line. You can then have him use his thumb. .
All of this will strengthen his digits and his hand. He will need these skills and the strength to have better control when writing. Also his visual attention will also become stronger.
Scissors, gluing with glue sticks, all will help build up these muscles.
Tracing paper on top of letters can help.
You could probably download some tracing sheets with letters, I used to purchase work books at book stores or at the teacher supply store.