This is a proven narration among Sunni fellows. We can understand how the Holy Prophet (PBUH) love Imam Ali(as), Lady Fatima(as), Imam Hassan(as) and Imam Hussain(as).

English Translation:

Sayyididina Ali ibn Abu Talib (RA) narrated: The Prophet held the hands of Hassan and Husayn and said,

‘He who loves me, loves these two, their father and their mother will be with me at my place on the Day of Resurrection”.

This hadith is graded as Hassan.

Here is another narration

Englisth Translation:

Sayyidina Usamah ibn Zayd (RA) narraterd: I went to the Prophet (SAW) one night in connection with a need. The Prophet came out wrapped in something. I do not know what it was. When I had finished what I had to, I asked,

‘What is this you are wrapped into?”

He uncovered it and they were Hasan and Husayn (RA) on his back. He said,

“They are my children-children of my daughter. 0 Allah, I love them, so do love them, and love whoso loves them,”

This hadith is graded as Hassan.

 

Here is another narration

Englisth Translation:

Abdur Rahman ibn Abu Nu’m reported that a man of Iraq asked Ibn Umar about blood of a mosquito that stains a garment. Ibn Umar (RA) said,

“Look at him. He asked about the blood of a mosquito while they have killed the son° of Allah’s Messenger(SAW). (We)had heard Allah’s Messenger (SAW) say. Surely, Hasan and Husayn are my two flowers in this world.”

This hadith is graded as Sahih. 

 

Here is another narration

Englisth Translation:

Bara reported that Allah’s Messenger observed Hasan and Husayn and said,

“0 Allah, I love them. So, do love them yourself.”

This hadith is graded as Hassan Sahih.

  

Here is another narration

Englisth Translation:

Sayyidina Bara ibn Aazib (RA) narrated. I saw the Prophet (SAW) place Hasan on his shoulder and make this supplication,

“0 Allah, I love him, so do love him yourself.”

This hadith is grade Hassan Sahih.