Is it permissible for us to sever ties of kinship if our blood-relatives` gatherings/meetings involve acts of sin?
                                Observing kinship ties is obligatory, and paying your blood-relatives a visit causing their sinful acts to be hindered , then you should do so. However, if their sinful acts continue while you are at their gathering and they didn't respond positively, then observing kinship ties via telephone and the like will suffice in this case. And Allah Knows 
                             
                        
                            
                                
                                Is it permissible for a person to give the Zakah (obligatory charity) to his daughter-in-law?
                                Yes, it is permissible for a person to give the Zakah to his daughter-in-law if she was poor, and none provided for particularly by whom are obliged to provide for her. And Allah Knows Best.
                             
                        
                            
                                
                                Is wearing a cap permissible for boys, or girls?
                                All Perfect Praise is due to Allah, The Lord of The Worlds.
In principle, anything is permissible sol long as there is no Sharia evidence prohibiting it, thus wearing the cap by boys is permissible as long as it isn`t done in imitation of the disbelievers. Moreover, a Muslim woman should avoid all that which attracts the attention of men because whatever leads to the forbidden is forbidden. And Allah Knows Best.
                             
                        
                            
                                
                                Is it permissible for a wife`s family to demand her husband to divorce her although she doesn`t want that?
                                It is forbidden for them to do that in case their daughter doesn`t want divorce unless there was a sin that continues as long as the marriage survives.