Here are the mistakes in each of the sentences:

1. **"There is four people in Mrs. Phong's family."**
- Correction: "There **are** four people in Mrs. Phong's family." (Use "are" for plural subjects.)

2. **"Does the children go to school in the morning?"**
- Correction: "Do the children go to school in the morning?" (Use "do" for plural subjects.)

3. **"The cat is among the lamp and the bed."**
- Correction: "The cat is **between** the lamp and the bed." (Use "between" for two items.)

4. **"There are two bookshelf in my sister’s bedroom."**
- Correction: "There are two **bookshelves** in my sister’s bedroom." (Use the plural form "bookshelves.")

5. **"My mother have short curly hair and big blue eyes."**
- Correction: "My mother **has** short curly hair and big blue eyes." (Use "has" for singular subjects.)

6. **"The cat is among the lamp and the bed."**
- Note: This sentence contains the correct word usage but requires the previous identification ("between").

These corrections address grammatical errors regarding subject-verb agreement, pluralization, and prepositions.