Grandparents are the parents of a person's father or mother – paternal or maternal.
It is allowed and he would probably be happy about the marriage, however, it is understandable if the family wishes to postpone it. Also, some cultures have viewpoints about these things (which are not specifically prescribed by Islamic law but could be taken into consideration although it is not required to adhere to cultural viewpoints).
What evidence does she have that she saw Virgin Mary herself or what she imagined as Virgin Mary?
Many people think and imagine according to their thinking. We can not take their claim as reality.
It's greatly noble that they are very good people, and for sure their nurturing contributed to your personality as well.
As you know, religion and becoming religious is a choice that must come from within. Even as Muslims, we always pray to Almighty God to keep us "guided" on the right path. Hidayah, or guidance is in the hands of the Almighty. If your grandparents, or anyone else around you has a potential that Allah ta'ala sees in them, then they will be guided to the light of Iman. If they do not "convert" to Islam, it does not mean they are evil, but just that hidayah is with the Almighty.
The best thing you can do is set yourself with high standards in your conduct, in your ambitions in life, and show those around you how a true Muslim should be.
That itself is a great form of conveying the message of Islam, and then it is up to them to investigate, or ask questions, and so on.
If you see that your grandparents are interested, or have questions, discuss what you know with them. However, never allow it to become an argument, or upset them, as they are your grandparents.
In any case, always do dua for yourself, your parents, your grandparents, your siblings and everyone else, that God showers them with His compassion and Mercy. Ask the Almighty to enlighten your hearts, and ask Him for guidance.
You can also do tawassul to Ahlul Bayt (a.s.), to give you the strength you need, and introduce them to Ahlul Bayt (a.s.), in a positive manner. You dont know what the outcome will be, but at least they will think positive of your religion, and understand you more.
With prayers for your success.
Yes. Grand mother of the wife is Mahram just like her real mother.
As she is not a Mahram for him, marriage with her is permissible if all other conditions are fulfilled.
If her father and paternal are dead, she will be allowed to marry a believer who is compatible to her in Religion and morals.
You need to keep the respect of your grand parents in every possible way, provided that your marriage choice is according to Islamic teachings. The objection of your grand parents does not invalidate the marriage if there is no valid reason for their objection.
It is the etiquette of Islam that beds are not shared with someone of a different gender, whether they be related or not.
In this particular situation, it would be better to sleep in the same room, but on a different bed, or alternative options.
And Allah knows best.
Imam Ja'far al-Sadiq (as) was a descendent of Abu Bakr through his mother. After Abu Bakr died, his wife Asma married Imam Ali, and thus Abu Bakr's son, Muhammad,was raised by 'Ali ibn Abi Talib. He became a staunch 'Alawi supporter, openly protesting against the corruption of the third caliph 'Uthman and taking part in the siege against 'Uthman's palace. He became a general in the army of Imam Ali, and fought for him at the Battle of the Camel (against Talha, Zubayr and his own sister Aisha) and at Siffeen against Mu'awiya (who had been made governor of Syria by 'Umar ibn Khattab). 'Ali ibn Abi Talib made him governor of Egypt during his short caliphate, but Ibn Abi Bakr was killed by the army of Amr ibn al-As who operated under Mu'awiya's governorship.
There is no difference in this regard between any of the grandchildren. As long as a child lives his or her children or the children of other siblings would not inherit.
He had this right to gift any of his property to anyone he wanted and it doesn't matter that he himself inherited these properties and didn't acquire them through his own endeavors
No, since the siblings are the entitled to the inheritance according to Sharia law.