Pakistan is a diverse mix of many different ethnicities, different people share different ancestors.
And what you must also understand is it is the backbone of our ideology which goes back from when the Mughals controlled India. Essentially we are modern day Mughals but with reduced territory.
To simply lump us all as having same origin as Indians is racist.
And how can they be our forefathers when we are alive today??? Surely if they had been killed or "forcibly converted" like you say then either we would not be alive today or have reverted back to Hinduism.
Perhaps Indians invaded neighboring territories and imposed themselves on the local population (like Kashmir) so maybe when the Muslim armies came they supported them and converted to Islam.