"My son has always been very independent."
Translation:Mi hijo siempre ha sido muy independiente.
'Ha' is the 3rd person auxillary verb for the present perfect tense. Él ha comido = he has eaten. The present perfect tense is formed from the present tense of 'haber' plus the past participle, with the -ado or -ido ending. This is almost exactly like English, which uses the present tense of 'have' plus the past participle with the -en ending.
'Hay' is a special form of 'haber'. It is used A LOT. It means 'There is...' as in 'Hay una mosca en mi sopa.' and 'No hay gasolina en el coche.' 'There are..' as in 'Hay cincuenta caballos en el campo' as well as in questions - '¿Hay un médico en la casa?' and '¿Cuántos peces hay en el océano?'
'Haber' is very irregular, and used constantly, so getting really familiar with all its forms is very useful.
Here is a Spanish verb conjugation site, which helps me keep these straight - http://www.spanishdict.com/conjugate/haber
Hope that helped!
I'd say "independent" is a personality trait, so it'd go with "ser". So you could say "Mi hijo siempre ha sido muy independiente, pero ahora, por su enfermedad, no (lo?) esta"= "my son has always been very independent, but now, due to his illness, he's not". His independende is permanent/a trait so you use ser. His lack of dependence is not permanent so you'd use estar.
(Not sure if it's "no lo esta" or just "no esta". have to look into that.)
I don't think that's correct. Generally in Spanish you can't separate ha and sido (or similar pairs) although I've seen it in certain situations. For example my gps is set up in Spanish and occasionally says 'la señal de gps ha se perdido'. It must be using the reflexive perderse. I think I've seen it in other contexts but best just to keep them together.