Regarding salary

1. Break up of salary will be available in your salary sheet. 
2. HRA will be exempted u/s 10(13A), only if you're paying rent. Otherwise, the entire amount paid as HRA will form part of salary and will be taxable. 
3. There is no criteria as such, that not claiming HRA will increase your basic salary. It depends upon the pay structure offered by your employer. 
Please correct me if the above solution has an alternative view. 

1. The wordings gave in sec 10(13A) is "residential accommodation occupied by the assessee". So rent paid by the assessee for his own residential accommodation will be covered under this section. 
2. Son staying in his own house and paying rent for his father's accommodation will not qualify for exemption u/s 10(13A). 
3. Exemption u/s 10(13A) will not be available to son. 
Please correct me if the above solution has an alternative view.