He could be initially shocked. Harry, who has trusted Ginny deeply, would find it hard to believe at first. He might go through a period of denial, trying to find excuses for Ginny's actions.
She might be heartbroken. Ginny could initially be in shock and disbelief. She may retreat into herself, spending a lot of time alone in her room, crying and trying to understand why Harry would refuse.
The Weasley family would be overjoyed. Molly Weasley would probably start crying tears of happiness and immediately start knitting things for their future home, like warm sweaters and cozy blankets. Arthur Weasley would be proud of Ginny and happy to have Harry as part of the family. He might even give Harry some old family wizarding artifacts as a sign of welcome.
Their friends from the Order of the Phoenix would be overjoyed and offer protection. Neville might give them some special plants that are good for a magical household with a baby. Luna would share her unique and sometimes strange but helpful insights about the baby's future.
He could also feel a great sense of anger. After the shock wears off, he might lash out at Ginny, demanding an explanation for her actions. His anger could be so intense that it might cloud his judgment for a while.
One great 'Harry Potter x Ginny' fanfic is 'Ginny's Time'. It delves into Ginny's perspective during the later years at Hogwarts. The story beautifully portrays her growth and her relationship with Harry. It shows how she becomes more confident and how their love story unfolds in a very natural way, with elements of mystery and adventure from the wizarding world.