The Maghrib prayer (Arabic: صلاة المغرب ṣalāt al-maġrib, '"sunset prayer"), prayed just after sunset, is the fourth of five obligatory daily prayers (salat) performed by practicing Muslims.
There may be some slight differences between the marajah, so it is important to check this with your specific Marja, but in general, the time of maghrib begins when the redness in the Eastern sky has dissipated.
Oftentimes, people think maghrib is when the redness of the western sky (where the sun sets) has dissipated but this is actually not the case and Maghrib occurs a bit earlier than this....
I would like to add that it is indeed recommended to perform one's prayer before breaking their fast, unless there is someone else waiting for them to break their fast, in which case it would be recommended to break fast with them, and then pray.
And Allah knows best.
Yes it is Mustahab(recommended) unless one is very weak, then it's better to do Iftar and pray afterwards
You can break your fast immediately at the time of adhan, if you are sure it is the correct time of adhan.
Thank you for your question. There is no problem with breaking your fast after the magrib prayers. In fact, in a tradition from Imam al-Sadiq (as) it is preferable to pray before breaking the fast.
May you always be successful.
Congregational prayer and prayer at the beginning of its time are both considered highly recommended in Islam. In "Wasa'il al-Shi'a" has been reported from one of the A'imma, peace be upon them, that congregational prayer is not mandatory but rather a sunna, however once it has been established it is not appropriate for the believer to abandon it with no valid justification to the point that Imam said: "Who abandons the congregation of the believers with dislike without any valid reason, in fact has not prayed". Another narration from the same source on the authority of Imam al-Sadiq, peace be upon him, says: "For each salat, there are two times and its first time is the best one. No one should delay it until its last time unless he has a valid justification". Regarding more specifically your question, considering that praying 10-20 minutes later may still be considered as "its first time" according to the 'urf, by waiting for your family you would get the blessing of both congregational prayer and prayer at the beginning of its time. You may also use those 10-20 minutes for preparing a suitable environment for the Jama'ah and recite some adhkar.
With prayers for your success.